Pipe joint restraint

ABSTRACT

A pipe joint restraint ( 16 ) includes a pocket ( 74 ) having a fulcrum ( 92 ) a fixed distance from the centerline ( 26 ) of an annular retaining gland ( 22 ) and about which a gripping element ( 76 ) pivots to move a gripping edge ( 75 ) toward the centerline ( 26 ) so as to grip a pipe ( 14 ) engaged by the gripping element ( 76 ) in response to thrust forces on the pipe ( 14 ). The length of gripping edge ( 75 ) is selected for the material of pipe ( 14 ). Adjustable element ( 78 ) operatively connects to the gripping element ( 76 ) and fulcrum ( 92 ) to pivot with the gripping element ( 76 ). Adjustable element ( 78 ) and may be torqued to a common, predetermined torque whether the pipe ( 14 ) is metal or polymeric.

This application claims priority to U.S. Provisional Patent Application60/587,565, filed Jul. 13, 2004, incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present invention relates generally to pipe joint restraints forcoupling the end of a pipe to another member, such as another pipe, avalve, or other similar members that are to be coupled with the pipe.

BACKGROUND OF THE INVENTION

It is often necessary to couple together the end of a pipe, such as awater pipe, to another member, such as another pipe, a valve, a fitting,or other similar pipe-like structure. In some cases, the ends of twoadjacent pipes may be flanged, and the flanges can be placed intoconfronting relationship to facilitate bolting the pipes together. Thiscoupling arrangement, however, is not always feasible or available.

A coupling device known as a mechanical joint, or MJ, can be used whereone of the pipes does not have an available flanged end. In thatsituation, the end of the non-flanged pipe is telescopingly receivedinto a flared end of a flanged member, with a following ring or annulargland situated over the pipe adjacent to the flange. A gasket isprovided which compresses into the pipe surface and against the flare ofthe other member to create a water-tight seal as the follower ring isbolted to the flange.

Mechanical joints are suitable for a number of situations, but may notbe able to retain the water-tight connection between the pipes where thepipes are subjected to hydraulic thrust forces which might tend to causethe pipes to telescope apart. To reduce the risk of the pipes comingapart, pipe joint restraints have been provided with the MJ or in lieuthereof. A pipe joint restraint typically has an annular retainer glanddefining a pipe-receiving space therethrough and having an axialcenterline. One or more pockets are associated with the annularretaining gland and have an open end confronting the pipe-receivingspace and a top wall radially outwardly of the opening. A grippingelement or wedge is movably supported in the pocket and has a grippingedge, such as a tooth, to frictionally engage the pipe surface when thegripping element is moved to project out of the pocket toward a pipe inthe pipe-receiving space. The gripping edge resists the tendency of thepipe to move away from the other member when the gland is bolted to theflange of the other member.

Conventionally, the frictional engagement of the wedges to the pipesurface resists separation of the pipe and the joined member. However,reliance on friction as the primary mechanism to hold the pipes togetherimposes significant requirements on the pipe joint restraint which canbe difficult to achieve in the field. By way of example, the grippingelement is moved into engagement with the pipe by a threaded bolt inoperative engagement with the wedge and the pocket such that as the boltis rotated, the wedge can be moved into the pipe surface. In order toprovide a sufficient hold to the pipe, however, it has been required totighten the bolt to relatively high torques, typically greater thanabout 65 to 75 or 90 foot-pounds for ductile iron pipes. These hightorques require more effort and exertion by the personnel who install orservice the pipes. These difficulties are compounded when personnel mustinstall pipes in the often inhospitable conditions of the outdoors, suchas freezing, wet, or muddy conditions, and in the tight spaces oftenexperienced in the field. Moreover, application of such high torques candeflect the pipe, making it difficult to maintain a seal. Often, theaxial bolts that secure the gland to the flange on the adjoining membermust be re-tightened to maintain a good seal. Moreover, the thrustforces may exceed the frictional ability of the joint to resistseparation of the pipe and the joined member.

Because piping systems may be formed from many different materials suchas metals (like ductile iron or steel, for example) or polymericmaterials such as polyvinyl chloride (PVC) or other plastic materials,and because each of these materials exhibits different properties andcharacteristics, different types of wedges are required to adapt pipejoint restraints for use with each of the different types of pipes. Forexample, pipes formed from ductile iron are much harder than pipesformed from polymeric materials, such as PVC. Accordingly, the surfaceareas contacted by the wedges, as well as the number of wedges and theparticular configuration of the gripping edges, may be considerablydifferent depending on the material from which the pipe is formed. Inaddition, the torque required to sufficiently secure the wedges to therespective types of pipes varies due to the differences in materialproperties of the pipes. Because pipes are also available in differentsizes, further variation in the configuration of the wedges is requiredto accommodate different sizes of pipe. To accommodate all of thesevarious configurations, manufacturers or suppliers must maintain aconsiderable inventory of different configurations of wedges andretainer glands, as well as the tooling needed to produce these variousconfigurations. Service and installation personnel might also have tokeep on hand several different types of retainer glands andcorresponding wedges to be able to work with the many differentvariations of pipes that may be encountered in the field.

SUMMARY OF THE INVENTION

The present invention provides pipe joint restraints that overcomedrawbacks of prior pipe joint restraints such as those described above.In some prior pipe joint restraints, the gripping element could pivotabout a fulcrum to provide a biting action to attempt to limit thrustmovement of the pipe. However, the fulcrum was defined, for example, atthe end of the adjustment bolt, which resulted in a movable fulcrumwhich in turn led to less than desirable securement to the pipe, andallowed the connection to fail if the bolt was not highly torqued. Ihave discovered that moving the gripping element toward the axialcenterline and relative to a fulcrum that is fixed a predetermineddistance from the centerline of the annular gland results in a much morereliable engagement with the pipe, and can achieve a secure connectionat much lower torque than previously thought possible, especially wherethe pipe is metal. To that end, and in accordance with the principles ofone aspect of the present invention, the top wall of the pocket definesa fulcrum fixed a predetermined distance from the axial centerline ofthe annular retainer gland, with the gripping element being operativelyengaged therewith so as to move relative to the fulcrum such that thegripping edge moves toward the centerline of the gland in response tomovement of the pipe along the axial centerline of the gland. Thatmovement is believed to result in a better engagement with the pipesurface as thrust tends to separate the pipes which in turn can betterresist further thrust movement of the pipe than did previous pipe jointrestraints.

Advantageously, the gripping element may pivot about the fulcrum. Thegripping element may be operatively engaged with the fulcrum via anadjustment member, such as a bolt, which pivots about the fulcrum withthe gripping element. When the gripping element is advanced toward thepipe surface by the adjustment member, the gripping element is disposedin a first orientation and grips the pipe by driving a gripping edgeinto the surface. When the pipes are subsequently exposed to hydraulicforces, the gripping element pivots about the fixed fulcrum to furtherdrive the gripping edge into the surface and thereby resist separationof the pipe from the member to which it is joined.

The bolt may include a shoulder that pivots about the fulcrum. To thatend, the top wall may include two planar surfaces extending oblique toeach other from a junction, with the fulcrum defined at the junction.Alternatively, the top wall may include two surfaces that define a steptherebetween, with the fulcrum being defined by the step. Additionally,or further alternatively, the top wall may include an arcuate surface ora protrusion on which the fulcrum is defined. A plurality of fulcrumsmay be defined thereon each being fixed a respectively predetermineddistance from the axial centerline of the gland.

In another aspect of the invention, a stop is associated with the pocketto limit how far the gripping element can pivot about the fulcrum. Thepocket may have an inwardly extending rear wall, with the stop definedthereon. The rear wall may be substantially perpendicular to an axialcenterline of the gland (and thus substantially perpendicular to thesurface of the pipe), or it may be oblique to the axial centerline ofthe gland. Advantageously, the gripping element may be pivotable betweena first position spaced from the stop and a second position contactingthe stop.

It is believed that movement into the pipe, such as by pivoting of thegripping element, about the fixed fulcrum formed in the top wall of thepocket creates an action resulting in a gripping of the pipe whichexceeds that attainable by previous pipe joint restraint devices. Inaccordance with a yet further aspect of the present invention, when abolt is used as the adjustment member, sufficient engagement between thegripping element and pipe may be achieved even for metal pipes at muchlower torques than previously thought reliable, such as 40 to 60foot-pounds, and advantageously about 45 foot-pounds.

In accordance with a still further aspect of the present invention, ithas been determined that the same level of torque may be applied toachieve a reliable grip for both metal or polymeric pipes by appropriateselection of the gripping element. To that end, a gripping element of afirst type for use with metal pipe may have a gripping edge of aparticular length, whereas a gripping element of a second type for usewith polymeric pipe may have a gripping edge that is similar to but isotherwise longer than the gripping edge of the first type.Advantageously, each gripping element has a laterally extending arm(extending in the circumferential direction of the annular retainergland), with the gripping edge disposed at least in part along the arm.The gripping elements may have different length arms, to thus providelonger or shorter gripping edges, to define the first and second typesof gripping elements. For example, the gripping element may haverelatively short arms when it is to be used with harder materials suchas ductile iron pipes, while relatively longer arms may be used forsofter polymeric material pipes, such as PVC pipes. The shorter armsresult in a relatively smaller contact surface on the pipe, therebyincreasing the stress between the gripping element and the pipe surface.This may be desirable when the pipe is formed from a harder material sothat the yield strength of the material can be exceeded to form a ridgeor groove within the surface of the pipe. Likewise, longer arms aretypically desired when the pipe is formed from relatively soft material,such as PVC or other polymeric materials. These longer arms help todistribute the stress between the gripping element and the pipe surfaceover a greater area, thereby avoiding excessive deformation of the pipematerial. By appropriate selection of the gripping element, it ispossible to use the same annular retaining gland for either a metal pipeor a polymeric pipe, to thus reduce inventory requirements. Moreover, inthe field, the torque requirements are substantially the same to createthe desired grip at a common, predetermined torque, namely about 40 to60 foot-pounds, and advantageously about 45 foot-pounds, when using theappropriate type of gripping element for the material of the pipe.Particularly with respect to ductile iron pipe, that predeterminedtorque is significantly less than previously thought necessary, while atthe same time not requiring any special differences in installation asbetween metal or polymeric pipes.

It is desirable to limit the torque that can be applied to theadjustment member to the common, predetermined and reduced level oftorques, such as 40 to 60, or advantageously, 45 foot-pounds. To thatend, and in accordance with a still further aspect of the presentinvention, the adjustment member may include a torque receiving portionthat separates from the adjustment member when the predetermined torqueis achieved. It will be appreciated that there are times when the pipejoint restraint must be removed from the pipe some time afterinstallation. However, with the torque receiving portion gone, looseningof the bolt may allow the parts to fall away from the gland after it isslid off the pipe end. To that end, the bolt may be provided with aninterior shoulder inside the pocket and an exterior shoulder outside thepocket which cooperate to retain the gripping element proximate thepocket even without a pipe in the pipe-receiving space. One of theshoulders may also cooperate with the fulcrum of the pocket top wall asdescribed above.

By virtue of the foregoing, there are thus provided pipe jointrestraints that overcomes drawbacks of prior pipe joint restraints.These and other objects and advantages of the present invention shall bemade apparent from the accompanying drawings and the descriptionthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the principles ofthe invention.

FIG. 1 is a cross-sectional view of a pair of pipes coupled together bya pipe joint restraint in accordance with the present invention;

FIG. 2 is a perspective view, from the back, of the pipe joint restraintof FIG. 1;

FIG. 3 is a partial cross-sectional view of one embodiment of a grippingelement pocket of the retainer gland of FIG. 2;

FIGS. 4A and 4B are partial cross-sectional views of the pipe jointrestraint and coupled pipes of FIG. I for purposes of explaining certainaspects of the present invention;

FIG. 5 is an exploded perspective view of a pipe engaging assembly ofthe pipe joint restraint of FIG. 1 and having a first type of grippingelement;

FIG. 6 is a perspective view of a second type of gripping element foruse in the pipe engaging assembly of FIG. 5;

FIGS. 7A-7C are partial cross-sectional views depicting an alternativeembodiment of a pipe joint restraint coupling a pair of pipes inaccordance with the principles of the present invention; and

FIGS. 8A-8C are cross sectional views depicting alternative embodimentsof gripping element pockets of the retainer gland of FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to FIGS. 1 through 5, there is shown an embodiment of apipe joint assembly 10 according to the various aspects of the presentinvention wherein the end 12 of a first pipe 14, such as a water mainpipe, is secured by a pipe joint restraint 16 to the end 18 of a secondpipe-like member 20 which may, for example, be another water main pipeor a pipe-like extension of a valve, fitting, fire hydrant, or othersimilar structure. Pipe joint restraint 16 has an annular retainer gland22 defining a pipe receiving space 24 therethrough and having an axialcenterline 26 (FIG. 2). Pipe end 12 is received into space 24 alongaxial centerline 26 such that gland 22 is disposed on the outer surface28 of first pipe 14. Gland 22 includes a front projecting rim 30 whichbutts up against an annular sealing member 32, such as a gasket,received on outer surface 28 of pipe end 12.

The end 18 of second pipe 20 is flared as at 34 to telescopingly receivepipe end 12 therein. A flange 36 of pipe end 18 may be held to gland 22with T-bolts 38 (only one shown) received through axially-extendingholes 40 and 42 on the gland 22 and flange 36, respectively. Gasket 32is in recess 44 coaxial with the flange 36 sized to receive a portion ofrim 30 so as to push gasket 32 into a water-tight sealing relationshipwith pipe surface 28 and pipe recess 44 as bolts 38 are tightened down.

Annular retainer gland 22 is secured to first pipe 14 by one or morepipe restraining mechanisms 50. Each pipe restraining mechanism 50 ispositioned adjacent an annular space 52 extending around the insidecircumference of retainer gland 22. The annular space 52 is defined by afront wall 54 and an adjacent, circumferential axially rearwardlyextending top surface 56. It is to be understood that the terms “top”,“front”, “rear”, and “bottom”, will be used solely as matters ofdefinition and are selected based on the orientation of the gland 22and/or mechanism 50. It will be apparent, therefore, that since theretainer gland 22 shown in FIG. 2 includes three of the mechanisms 50,the terms “top”, “front”, “rear”, and “bottom” do not necessarily referto actual positions in the retainer gland. Rather, bottom is meant torefer to a direction towards the pipe-receiving space 24, and top isradially outwardly thereof as seen in FIG. 2, whereas front refers tothe direction towards the end 12 of first pipe 14, i.e., towards secondpipe 20, and rear (or back) is in the opposite direction axially spacedaway from the front as seen in FIG. 1.

In the exemplary retainer gland 22 shown in FIG. 2, threecircumferentially spaced mechanisms 50 are depicted, However, the numberof mechanisms 50 may vary as required for a particular application.Because the three mechanisms 50 shown are identical in construction,specific details of only one mechanism 50 will be described. Each piperestraining mechanism 50 includes a pocket housing 60 (FIG. 3)associated with gland 22 such as by being integrally formed therewithand a pipe engaging assembly 62 (FIG. 5) cooperatively coupled to pockethousing 60. Pocket housing 60 has an open bottom 64 (FIG. 3) confrontingpipe-receiving space 24, a top wall 66 radially outwardly of opening 64,front wall 68, rear wall 70 and two sidewalls 72 (only one shown in FIG.3) to define therebetween a pocket 74. Each pipe engaging assembly 62(FIG. 5) includes at least a gripping edge 75 supported on a grippingelement 76, also referred to as a wedge, an adjustment member 78, whichmay advantageously be in the form of a rigid, elongated collar bolt (¾inch diameter-10 UNC threads per inch), and a hollow nut 80 to receivetorque to adjust bolt 78. Gripping element 76 is received in pocket 74defined within pocket housing 60 such that at least a top portion 82 ofwedge 76 is moveable within pocket 74. Bolt 78 has a top shank portion84 extending outside of the pocket 74 and a threaded shank portion 86extending into and at least partially within pocket 74. Wedge 76 may beinserted into pocket 74 through bottom opening 64 and has a threadedhole 88 extending radially at least partially therethrough to bethreadably engaged with threaded portion 86 of bolt 78. As will beappreciated, rotation of bolt 78, such as via nut 80, causes wedge 76 tomove radially toward or away from top wall 66 of pocket 74. Wedge 76 hasat least one gripping edge or tooth 75 so as to engage pipe surface 28when wedge 76 is moved toward pipe 14 as seen in FIG. 4A, and tothereafter bite into pipe surface 28 in response to thrust forcestending to move pipe ends 12, 18 telescopingly apart such as alongcenterline 26 as seen in FIG. 4B. In the embodiment shown in FIG. 5, twoteeth 75 are provided.

With particular reference to FIG. 3, top wall 66 of pocket 74 contains anon-threaded through-hole 90 with portion 84 of bolt 78 projectingtherethrough, a front bearing surface 66 a, and a rear bearing surface66 b. The front bearing surface 66 a is substantially planar andparallel to the axial centerline 26 of the gland 22 (and, consequently,to the surface 28 of a first pipe 14). The rear bearing surface 66 b isalso substantially planar but oblique to the front bearing surface 66 aso as to be inclined towards the top and back with respect to the axialcenterline 26. The front and rear bearing surfaces 66 a, 66 b intersectat a juncture 92 approximately at the centerline of the through-hole 90,creating a fulcrum thereat (i.e., at 92) at a fixed distance from axialcenterline 26 of gland 22 and about which gripping element 76 may moveor pivot as will be explained.

With particular reference to FIG. 5, adjustment member bolt 78 has acollar 94 between a non-threaded shank 84 and threaded shank 86 andadapted to be within pocket 74. Collar 94 is larger than hole 90 so asto pivotably bear against top wall 66 without coming out through the topwall 66. The threaded shank 86 may, if desired, terminate in anon-threaded tip 96 of smaller diameter than the minor thread diameterof the threaded shank 86. The non-threaded tip 96 may contain a groove98 for receiving a retaining snap ring 100 (FIG. 1). The retaining snapring 100 is wider than the diameter of wedge hole 88 and 50 acts as alimit to travel of the gripping element 76 along the threaded shank 86toward pipe receiving space 22 to thereby minimize or prevent overdeflection of the surface 28 of pipe 14 when moving gripping element 76into engagement with pipe surface 28 (FIG. 4A). When gripping element 76and particularly gripping edge(s) 75 thereof, are in contact with pipesurface 28 as seen in FIG. 4A, thrust forces that tend to propel thepipes 14 and 20 apart telescopingly cause pipe end 12 to move towardsthe rear (in FIG. 1). That tendency to rearward movement causes grippingelement 76 to move from a first angular orientation, such as with hole88 perpendicular to centerline 26 as seen in FIG. 4A, to a secondangular orientation with hole 88 oblique to centerline 26 as seen inFIG. 4B such that gripping edge 75 has moved towards centerline 26. Inparticular, gripping element 76, via bolt 78 and collar 94, isoperatively engaged with fulcrum 92 so as to move relative thereto suchthat the gripping edge 75 moves toward centerline 26 in response tomovement of pipe 14 along centerline 26 with gripping element 76 engagedwith pipe 14. The gripping element 76 is most advantageously pivotalabout fulcrum 92 which is fixed relative to centerline 26 so as toenhance the biting affect of gripping edge 75 to pipe surface 28. Aspipe 14 tends to thus move, bolt 78 pivots about fulcrum 92 withgripping element 76 such that collar 94 tilts from bearing contact withsurface 66 a into bearing contact with surface 66 b, to thus pivotgripping element 76 in the direction of movement of pipe 14. That pivotaction also serves to restrain further rearward movement of pipe 14against the encountered thrust forces so as to hold the pipe ends 12, 16fluidicly together.

A stop 102 associated with the pocket 74 limits the rotational movementof the gripping element 76 from the first position (FIG. 4A) spaced fromstop 102 to the second position (FIG. 4B) contacting stop 102. In theembodiment shown, stop 102 is defined on, and by, the rear wall 70 ofthe pocket 74. Alternatively, a stop that limits the rotation of thegripping element may be provided on other portions of the pipe jointrestraint 16. In the embodiment shown, the rear wall 70 extends radiallyinwardly toward the pipe receiving space 24 and axially rearwardly so asto be substantially perpendicular to the rear bearing surface 66 b andtherefore inclined obliquely to a direction that is perpendicular to theaxial centerline 26 of the gland 22.

Each sidewall 72 extends from the top wall 66 toward the open bottom 64,and between the front and rear walls 68, 70. The sidewalls 72 may eachcomprise first and second sidewall sections 72 a, 72 b with secondarybearing surfaces 104 positioned therebetween. These secondary bearingsurfaces 104 act as secondary stops that further limit pivoting movementof the gripping element 76 toward the second position. The firstsidewall sections 72 a extend from the front bearing surface 66 a andslope away from the front bearing surface 66 a outwardly toward theannular space 52.

In the embodiment shown, the non-threaded shank 84 contains acylindrical portion 105 above shoulder 94 (FIG. 4A) and sized to fitrotatably with hole 90 of top wall 66, a hexagonal secondary drivinghead 106, and a rectangular cross section primary driving head 108.Secondary driving head 106 fits rotatably within bottom opening 110 ofnut 80, and primary head 108 fits snugly within top, rectangular slot112 of nut 80 such that rotation of nut 80 translates torque throughhead 108 to rotate bolt 78. Driving head 108 terminates in a V-shapedstake 114 extending beyond the top 115 of hollow nut 80. The legs 114 a,114 b of the V-shaped stake 114 may be forced apart during assembly overthe top 115 of nut 80 to thereby retain the nut 80 on the non-threadedshank 84, and consequently retain the gripping element 76 and theadjustment member 78 with pocket 74 during shipment and subsequentinstallation on the pipe 14. While the embodiments shown herein havebeen depicted with a nut staked to the primary driving head 108, it willbe recognized that other methods may be used to secure the nut 80 to theprimary driving head 108. Before applying nut 80, a lockwasher 120 maybe force-fit over secondary head 106 to serve as an external shoulderfor purposes to be described hereafter.

Rectangular cross-section primary driving head 108 is adapted to breakor twist off when the torque applied to the collar bolt 78 via nut 80exceeds a predetermined torque, thus limiting the torque on bolt 78 toabout the predetermined amount. In one embodiment, the predeterminedtorque is not more than about 40 to 60 foot-pounds. In anotherembodiment, the predetermined torque is not more than about 45foot-pounds. As a result, the nut 80 serves as a torque receivingportion that separates from bolt 78 to limit tightening of bolt 78 toapproximately the predetermined torque.

Lockwasher 120 is external of pocket 74 and remains secured to theadjustment member 78 after hollow nut 80 is separated from bolt 78. Thelockwasher 120 thus defines a shoulder exterior of the pocket 74 andcooperates with the collar 94, which defines a shoulder interior of thepocket 74, to retain the bolt 78, and gripping element 76 thereon,proximate the pocket 74 if the retainer gland 22 is subsequently removedfrom the pipe 14 (which can be achieved by loosening bolt 78 viasecondary head 106). While the embodiments shown and described hereininclude shearable driving head 108 to limit the torque applied to theadjustment member, it will be recognized that various other methods oflimiting the applied torque may alternatively be used.

Hole 88 of the gripping element 76 includes internal threads 122 tomatch the external threads 124 on the threaded shank 86. The internalthreaded portion 122 extends radially outwardly partially through thegripping element 76 from above the bottom face 125 thereof with thebottom-most portion defining a non-threaded tapered portion 126 (FIG. 5)that is larger in diameter than the major diameter of the threadedportion 122 and sized to receive therein the retaining snap ring 100.However, as will be appreciated, mechanism 50 is adapted, such asthrough use of driving head 108, to limit torque such that snap ring100, and the associated structural variations to bolt 78 and hole 88 toaccommodate snap ring 100, may not be necessary.

Positioned radially below bottom face 125 is an arcuate bottom arm 130supporting the gripping edge(s) 75. Arm 130 is adapted to move towardengagement with pipe surface 28 as edge(s) 75 engages thereat (FIG. 4A).Where pipe 14 is of a polymeric material, the gripping edge(s) 75 andthe arm 130 supporting same are relatively long and fitcircumferentially into annular space 52 well beyond the perimeter ofpocket 74. Where the pipe 14 is of metal, such as ductile iron, thegripping edge(s) 75 can be shorter, and so they may the arms 130 beshorter, as at 130′ in FIG. 6, so as to be more closely confined near orwithin the footprint of pocket 74 at open bottom 64. While two grippingedges 75 are shown in FIG. 5, it will be recognized that grippingelement 76 may have only one gripping edge 75, as depicted for grippingelement 76′ in FIG. 6, or may have three or more such edges. The lengthof the gripping edges 75 and thus arms 130, 130′ may be selected, asrequired, to accommodate pipes made from different materials.

Relatively longer gripping edges 75 may be desired for use with pipesformed from soft materials, such as PVC or other polymers, so that thecontact stresses between the gripping element 76 and the pipe are spreadover a wider area, while shorter, but otherwise similar, gripping edges75 may be desired for use with relatively harder pipes, such as ductileiron or other metals, where the reduced contact area between thegripping edges 75 and the pipe helps to overcome the yield strength ofthe pipe material so that an adequate bite, such as a deflection ofsurface 28 and/or formation of a groove in pipe surface 28 as at 132(FIG. 4B). For pipes 14 nominally referred to by AWWA standards as being6″ to 12″ in size, the radial depth of each tooth 75 (which is at a 35°angle) may be about 0.10 inch, or about 0.07 inch for 4″ pipe. The tooth75 is intended generally to conform to the circumference of pipe 14, todefine a cord length between the outer tip ends 75 a, 75 b thereof. Thecord length for polymeric pipes may be about 4.40 inches for 6″ pipe and4.50 inches for 8″ pipes. For 4″ pipes, the cord length may be about4.30 inches, but the tooth is curved to subtend an angle of 138° of thepipe circumference. For metal pipes, a 2.3 inch cord length may beselected for pipe sizes of 4″ to 12″ and possibly larger pipes.

In the embodiments shown, the side portions 134 of arms 130 or 130′extending to either side of hole 88 may extend beyond the sidewalls 72of the pocket 74 and along the annular space 52 to provide secondarybearing areas for contact with sidewall secondary stops 104.

While two embodiments of gripping element 76, 76′ are shown herein, itwill be recognized that various other configurations of grippingelements may be used with a pipe joint restraint in accordance with thepresent invention. In any event, selection of the appropriate sizedretainer gland 22 and number of mechanisms 50, with selection from atleast the two different types of gripping elements 76 or 76′above-described (which differ primarily in the length of edges 75 and/orarms 130, 130′ supporting same), facilitates use of the pipe jointrestraint 16 with various pipe materials, such as pipes formed fromductile iron, polymeric material, or other materials, merely by suchproper selection. The annular gland 22 will be selected to have a pipereceiving space 24 (the ID of gland 22) matched to the OD of pipe 14.For example, the ID of gland 22 for a 3″ pipe is about 4.06 inches andfor a 6″ pipe is about 7.0 inches so as to accommodate the variations inOD of pipes based on steel or ductile iron standards. However, becausethe retainer gland 22 has a non-cored annular space 52 which extendscircumferentially around the gland, different types of gripping elementshaving different length arms 130, 130′ may be accommodated by theretainer gland 22.

Additionally, and in accordance with another aspect of the invention,pipe restraining mechanism(s) 50 allow operation with either metal orpolymeric pipe 14 with a common, predetermined torque being applied tonut 80 sufficient to cause gripping element 76 or 76′ to adequatelyengage the surface 28 of pipe 14, regardless of the material used toform the pipe. In one embodiment, the predetermined torque is not morethan approximately 40 to 60 foot-pounds. In another embodiment, thepredetermined torque is not more than approximately 45 foot-pounds. Thistorque value is substantially less than the torque conventionallyrequired for restraining pipes with prior pipe joint restraints,especially where the pipe was of ductile iron. Thus, in the field, nospecial training or equipment is necessary between polymeric or metalpipes, as the same, or a common, torque is to be applied and the nut 80breaks away thereat such that selection of the type of gripping element(e.g., 76 or 76′) is the primary factor to be decided.

FIGS. 7A-7C, shows a modified version of pipe restraining mechanism 50′where like parts to mechanism 50 bear like numbers. As can be seen,mechanism 50′ differs from mechanism 50 primarily in that the cylinderportion 105′ of bolt 78′ has a castellated rim 140 extending throughnon-threaded through-hole 90 in the top of pocket 74 and a resilientwasher 142 is fitted over the castellated rim 140. Resilient washer 142serves to retain the adjustment member bolt 78′ in a positionsubstantially perpendicular to the axial centerline 26 duringinstallation on the pipe 14. As the hollow nut 80 is pressed down ontothe primary driving head 108, the bottom surface 144 of the nut 80engages the castellated rim 110, deforming and spreading the rim 110outwardly as seen in FIGS. 7B (before nut 80 is sheared off) and 7C(after nut 80 has been removed). The castellated rim 140 consequentlyretains the resilient washer 142 as a shoulder of bolt 78′ outside ofpocket 74 to thus hold gripping element 76 and adjustment member bolt78′ with the pocket 74.

Referring now to FIGS. 8A-8C, there are shown alternative wedge pocketembodiments in accordance with certain aspects of the invention. In FIG.8A, the wedge pocket 60 a is depicted with a top wall 150 having aconvex surface which defines plurality of fulcrum positions (only threeshown at 150 a, 150 b, and 150 c) each being a respective fixed distancefrom centerline 26 and about which the adjustment member 78 and grippingelement 76 are sequentially pivoted in response to thrust forces, asdescribed above. Depending on the radius of curvature of the convexsurface, there may be only one fulcrum 150 a, or there may be aplurality of fulcrums (150 a, 150 b, 150 c), each a respective fixeddistance from the centerline 26 of retainer gland 22. As a furtheralternative, rear wall 70′ is substantially perpendicular to thecenterline 26 of the retainer gland 22 rather than oblique thereto. FIG.8B depicts another embodiment 60 b wherein the top wall 160 includes abump or ridge 162 to define at least at the bottom apex 164 thereof, thefixed fulcrum of the pocket 60 b. In use, the shoulder 94 of theadjustment member 78 abuts the ridge 162 and pivots about the apexfulcrum 164 in reaction to thrust forces developed in the pipe, asdescribed above. FIG. 8C depicts yet another embodiment 60 c wherein thetop wall 170 comprises two surfaces 170 a, 170 b having a step 172formed therebetween. The step 172 defines the fixed fulcrum and aboutwhich gripping element 76 pivots in a manner similar to that describedabove.

With the present invention, pockets 74 may be the same whether two ormore mechanisms 50 are to be formed with gland 22 and irrespective ofthe sizing of gland 22 such that the same core design can be used. Witha particular size gland 22 for a selected pipe size, the same number ofmechanisms 50 may be used for metal or polymeric pipe by selection ofthe type of gripping element so as to have the desired length ofgripping edge 75. For example, in the 3″ to 6″ size of pipe, only onegripping element 76, 76′ may need to be used for every two bolts 38required for the standardized MJ. For larger pipe sizes, threemechanisms 50 will usually suffice although four or more may be desiredfor the largest pipe sizes. The gland 22 may be provided with grippingelements 76 and/or 76′ for plastic and/or metal pipes, such that gland22 is a multiple use gland by providing different types of grippingelements.

In use, gland 22 is placed on surface 28 at the end 12 of pipe 14, andgasket 44 is fitted over pipe end 12. End 12 is telescoped into pipe end14, and gland 22 bolted to flange 36. Nut(s) 80 is rotated to bringteeth 75 into engagement with surface 28 and may be tightened until itshears off at about the predetermined torque. Pipes 14, 20 may then bepressurized with subsequent hydraulic thrust forces which tend to movepipe 14 along centerline 26 acting to pivot gripping elements 76 tocause teeth 75 to move into and bite into surface 28 to thus resist suchmovement.

By virtue of the foregoing, there are thus provided pipe jointrestraints that overcome drawbacks of prior pipe joint restraints.

While the present invention has been illustrated by the description ofthe various embodiments thereof, and while the embodiments have beendescribed in considerable detail, it is not intended to restrict or inany way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethods and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope or spirit of Applicant's general inventive concept.

What is claimed is:
 1. A pipe joint restraint comprising: an annularretainer gland defining a pipe-receiving space therethrough and havingan axial centerline; at least one pocket associated with the annularretaining gland and having an opening confronting the pipe-receivingspace and a top wall radially outwardly of the opening, the top walldefining at least one fulcrum fixed a predetermined distance from theaxial centerline of the annular retainer gland; a gripping elementhaving at least one gripping edge adapted to engage a pipe received inthe pipe-receiving space; an adjustment member extending within thepocket and threadably coupled to the gripping element, wherein theadjustment member is pivotable about the at least one fulcrum with thegripping element such that the at least one gripping edge moves towardthe axial centerline of the annular gland in response to movement, alongthe axial centerline of the annular gland, of a pipe received in thepipe-receiving space and engaged by the at least one gripping edge ofthe gripping element; a stop associated with the pocket, the stoplimiting pivotal movement of the gripping element about the at least onefulcrum; and the at least one pocket further including a rear wallextending radially inwardly from the top wall, the stop defined on therear wall.
 2. The pipe joint restraint of claim 1, the gland furtherincluding a plurality of bolt holes for receiving bolts to fasten thegland to a flange of a member receiving an end of a pipe received in thepipe-receiving space of the gland.
 3. The pipe joint restraint of claim1 further comprising a plurality of said at least one pockets associatedwith the retainer gland.
 4. The pipe joint restraint of claim 1, thegripping element being pivotable about the at least one fulcrum in adirection substantially corresponding to the direction of pipe movement.5. The pipe joint restraint of claim 1, the gripping element pivotablebetween a first position spaced from the stop and a second positioncontacting the stop.
 6. The pipe joint restraint of claim 1, the rearwall extending substantially perpendicularly to the axial centerline ofthe retainer gland.
 7. The pipe joint restraint of claim 1, the rearwall being oblique to the axial centerline of the retainer gland.
 8. Thepipe joint restraint of claim 1, the gripping element having a firstangular orientation when the at least one gripping edge initiallyengages a pipe received in the pipe-receiving space, the grippingelement having a second different angular orientation when the grippingelement is moved relative to the at least one fulcrum.
 9. The pipe jointrestraint of claim 1, the adjustment member being adapted to move thegripping element relative to the top wall.
 10. The pipe joint restraintof claim 1, the adjustment member being rigid.
 11. The pipe jointrestraint of claim 1, further comprising an aperture formed in the topwall for receiving a portion of the adjustment member therethrough, theadjustment member including an interior shoulder inside the pocket andan exterior shoulder outside the pocket, the interior and exteriorshoulders cooperating to retain the gripping element proximate thepocket without a pipe in the pipe-receiving space.
 12. The pipe jointrestraint of claim 1, the gripping element being one of a first type ora second type, the first type having at least one gripping edge with afirst length and configured for use with a metal pipe, the second typehaving at least one gripping edge with a second length longer than thefirst length and configured for use with polymeric pipe.
 13. The pipejoint restraint of claim 12, the gripping element having a laterallyextending arm, at least a portion of the gripping edge disposed on thearm.
 14. The pipe joint restraint of claim 13, the retainer glandfurther including a recess extending circumferentially around the gland,wherein the recess is defined by a wall and an adjacent, circumferentialaxially extending surface, wherein the circumferential axially extendingsurface terminates at a radially innermost edge of an outer face of thegland, the arm of the gripping element receivable in the recess wherebyvarious length gripping element arms may be accommodated by the retainergland.
 15. The pipe joint restraint of claim 12, further comprising anadjustment member operatively engaging the gripping element and the atleast one fulcrum, and being threadably coupled to the gripping element,the adjustment member being pivotable about the at least one fulcrumwith the gripping element, and wherein the adjustment member includes atorque receiving portion that separates from the adjustment member tolimit tightening of the adjustment member to a predetermined torque. 16.The pipe joint restraint of claim 15, wherein the predetermined torqueis not more than approximately 60 foot-pounds.
 17. The pipe jointrestraint of claim 16, wherein the predetermined torque is not more thanapproximately 40 foot-pounds.
 18. The pipe joint restraint of claim 15,wherein the predetermined torque is not more than approximately 45foot-pounds.
 19. The pipe joint restraint of claim 1, the top wallincluding an arcuate surface, the at least one fulcrum defined on thearcuate surface.
 20. The pipe joint restraint of claim 19, including aplurality of fulcrums on the arcuate surface.
 21. The pipe jointrestraint of claim 1, the top wall including at least two surfacesdefining a step therebetween, the at least one fulcrum defined by thestep.
 22. The pipe joint restraint of claim 1, the top wall including apair of planar surfaces extending oblique to each other from a junction,the at least one fulcrum defined at the junction.
 23. The pipe jointrestraint of claim 1, the top wall including a protrusion extending fromthe top wall in a direction radially inwardly of the retainer gland, theat least one fulcrum defined by the protrusion.
 24. A pipe jointrestraint comprising: an annular retainer gland defining apipe-receiving space therethrough; at least one pocket associated withthe annular retaining gland and having an opening confronting thepipe-receiving space and a top wall radially outwardly of the openingand said top wall having an aperture; a gripping element having at leasta portion moveable within the at least one pocket and at least onegripping edge for engaging a pipe received in the pipe-receiving space;and an adjustment member extending into the at least one pocket throughthe top wall aperture so as to operatively engage the gripping element,the adjustment member including an interior shoulder inside the at leastone pocket, an exterior shoulder outside the at least one pocket, andnut outside the at least one pocket, wherein the nut is configured toreceive torque to rotate the adjustment member, and wherein the exteriorshoulder is configured to contact the pocket top wall to retain thegripping element proximate the at least one pocket when the nut isremoved from the adjustment member.
 25. The pipe joint restraint ofclaim 24, the exterior shoulder being defined by a lockwasher.
 26. Thepipe joint restraint of claim 24, the exterior shoulder being defined bya castellated rim.